The embodiments described herein relate generally to an x-ray diffraction imaging (XDI) system and, more particularly, to an XDI system with an integrated supermirror.
Known security detection systems are used at travel checkpoints to inspect carry-on and/or checked bags for concealed weapons, narcotics, and/or explosives. At least some known security detection systems include x-ray imaging systems. In an x-ray imaging system, an x-ray source transmits x-rays through an object or a container, such as a suitcase, towards a detector, and the detector output is processed to identify one or more objects and/or one or more materials in the container.
At least some known security detection systems include an XDI system, e.g., a multi-detector inverse fan beam (MIFB) XDI system that uses an inverse fan-beam geometry (a large source and a small detector) and a multi-focus x-ray source (MFXS). At least some known XDI systems provide an improved discrimination of materials, as compared to that provided by other known x-ray imaging systems, by measuring d-spacings between lattice planes of micro-crystals in materials. Further, x-ray diffraction may yield data from a molecular interference function that may be used to identify other materials, such as liquids, in a container.
Known MIFB XDI systems feature an x-ray multisource emitting a multiplicity of x-ray beams, such that each object voxel is irradiated from several different directions, and such that these systems measure spatially-resolved x-ray diffraction profiles of the constituent voxels of inhomogeneous, extended objects. An important requirement of x-ray screening, whether for solid-state, liquid, amorphous or other types of explosives, is to enhance the detection performance while reducing the false alarm rate. MIFB XDI systems have an intrinsically excellent detection performance when the number of detected scatter photons is large. However, to attain the necessary x-ray flux, such systems typically require high electric power draws for the associated high-powered x-ray sources, and this electric power must be provided at the location where the XDI screener is operated. This because the x-rays are generated by point x-ray sources and these x-rays are subject to divergent emission.
The use of mirrors to reflect x-rays that otherwise would be lost due to normal fanning of x-rays has been considered. The mirrors would facilitate increasing the x-ray flux by directing the fanning x-rays into a parallel x-ray beam, thereby decreasing the requirements for high electric power draws. The use of supermirrors to reflect even a greater number of x-rays in a coherent manner facilitates further reductions in the power draw. Known supermirrors are depth-graded multi-layer mirrors that include a layer of glass upon which is formed a plurality of alternating layers of high-density and low-density material, such as tungsten and silicon. These supermirrors have a mirrored face directed towards the x-rays and an uncoated face on the side opposite the x-rays. Such supermirrors are typically used in x-ray telescopes to enhance the x-ray flux collected for astronomical observations. However, known configurations for such supermirrors include a framing system that holds the mirrors “face-on” at the uncoated face. As such, these known configurations of the supermirrors are incompatible with many known XDI MIFB topologies that include a plurality of planes of x-rays extracted from the same x-ray sources without adding additional sources. As such, the adjacent x-ray planes are too close to each other to allow a face-on mirror frame structure.